Improved methods for prevention of dental caries and periodontitis are badly needed. A major problem is the administration of potentially effective drugs in such a manner that optimum concentrations are maintained in the oral cavity for a long enough time. The objective of this proposal is to develop devices that deliver small amounts of an antimicrobial compound at constant rates such that effective levels can be maintained for prolonged and controlled periods of time. The devices will be either flat or cylindrical in shape and small, so that they eventually can be adapted for placement in the oral cavity. They will consist of a core containing the antimicrobial agent and an outer layer to control the release of the drug. The antimicrobial compound chosen for this investigation is chlorhexidine. The controlling membrane will be ethylene vinylacetate copolymer (EVA). The vinylacetate content of these membranes determines the rate at which chlorhexidine is released. The permeability of a range of membranes with different vinylacetate contents will be determined to select those suitable for the fabrication of devices. The in vitro release rate of chlorhexidine from complete devices will be determined spectrophotometrically. The in vitro antimicrobial effect of devices with known release rates will be tested against artificial plaques grown on stainless steel wires. For comparison, artificial plaques will also be exposed to brief rinses with chlorhexidine solutions. The release rate of the drug from the devices will be followed for a prolonged time. Also the physical and chemical stability of the devices will be determined for at least a year to establish the shelf life of the dosage form.